Good day,
I am currently using your I2C (LPS25HB) pressure sensors and working on a project where I need to take multiple measurements simultaneously. I have looked into multiplexers but found that these multiplexers switch between the sensors and do not concurrently record the values from the sensors. My sensors will be placed onto a high-speed fan and thus I require the readings to be synchronized. I want to connect up to 16 sensors.
Could you possibly assist me with a product that will be able to do this? I have read into your NodeLynk devices but found nothing on the speed of the devices.
I would appreciate your help in understanding how these devices work and also what you would recommend for the situation.
The LPS25HB only has one configurable I2C bus address bit. This means only 2 LPS25HB can be used on a single I2C bus. It is possible to use an I2C Bus multiplexer such as the PCA9547 which would give 8 I2C busses, meaning you could have up to 16 LPS325HB sensors. This would require setting the bus of the multiplexer, reading the 2 sensors on that bus, then switch to the next bus, read those 2 sensors, and so on. This switching is quite fast, I’m sure the PCA9547 data sheet has some information on possible switching speed. It would be good to know how quickly you need to obtain readings from all 16 sensors(maximum latency).
Hi Travis,
Yes, I have seen that the multiplexers are available. It is an option I am considering.
Ideally, I want to take all of the measurements at exactly the same time, but I have not yet found an option that allows this. If you know of something that would be appreciated.
Regarding the multiplexer that you mentioned above. I found that it operates at a clock frequency of 400kHz. This is good if nothing else is available. I also saw on the website the " I2C Converter with Dual Serial to 8-Port Hardware I2C" which can operate at a clock frequency of 700kHz. Does this fulfill the same function as the multiplexer? Also, if I would like to use either of these options, what are all the components that are required to make it work?
Theoretically it is not 100% possible to read all sensors on an I2C bus at the same time. Each must be addressed individually. I highly doubt you find a reasonable solution to read all 16 points at exactly the same millisecond. There has to be some latency allowance.
Your " I2C Converter with Dual Serial to 8-Port Hardware I2C", device. Does this provide the same function as the multiplexer, just with the communication to the PC included? Is it possible to use this device without a microcontroller and only use a microcontroller as the receiver of the data?
Yes, That is basically an I2C bus multiplexer connected to a processor that runs custom firmware that interprets commands over the serial interfaces to relay accordingly to the I2C ports.